Quantics

P. O. Box 2163

Nevada City, California 95959-2163

W9GR Digital Signal Processors

As Published in QST Magazine
and the ARRL Handbook

Entire contents copyright (c) 1997-2012 by
Quantics

updated November 2012

We are sorry to announce that
the DSP-3 digital signal processor is SOLD OUT! Texas
Instruments, the manufacturer of the DSP CPU and audio codec
chips we use, has obsoleted these parts. So, since we can't buy
the key parts of the DSP-3 anymore, there will be no more DSP-3s.

I really would like to do a
DSP-4, using a more modern DSP chip that would hopefully stay in
production for more than a few years. I've been planning on doing
one since the DSP-3 went out of production. Unfortunately, many
things have been distracting me from doing a DSP-4 design - more
construction projects (barn and driveway), my day job (designing
digital TV transmitters), etc. I can't really put a timetable on
the DSP-4 development or even guarantee that it will ever happen.
All I can say right now is that it is something that I would like
to do. So, keep an eye on this web page, and check in every six
months or so to see if I have anything to announce.

We will leave this web page up,
even though it describes a product which is no longer available.
Most or all of the features in the DSP-3 will be offered in the
DSP-4, along with some new features.

If we receive any more orders
for the DSP-3, we will have to return them to you. Thank you for
your patience in waiting for the DSP-4!

What is this thing? It's a powerful digital signal processor
("DSP") using advanced algorithms to remove noise and
other unwanted interference from voice and data communications
signals. It is sold in kit form. It connects between your ham
radio's audio output and your loudspeaker.

If you haven't used Adobe's Acrobat, it presents the PDF file
in a magazine-like format. You can look at a multiple page
document, zoom in, zoom out, look at embedded graphics, all with
very good resolution. With Acrobat, you can also print out the
DSP-3 schematic in any size. The viewer is a free download from
Adobe and is available in several formats: UNIX, Windows, OS/2
and Macintosh. PDF files are quite universal. Just use the link
below and download your flavor of Acrobat and then download the
PDF files from this page and to view them. (Note: if you just
click on the PDF files above, Acrobat will load them
immediately. But if you SHIFT-click, you can download the PDF
file to your hard disk for later viewing.)

Would you like to hear some of the amazing things this DSP can
do to clean up crummy radio signals? What follows are some sound
(.WAV) files (sound bytes!) you can download and listen to. Each
of these sound files contains several seconds of unprocessed
audio, followed by the same audio after it has been processed
through the DSP. So what you will be hearing will be a
"before/after" comparison. These files are short to
keep transmission time down and file size moderate.

All of these files are 8 bits, 8 kHz sampling, also to keep
file sizes down. (Some older sound cards, which do not have
lowpass reconstruction filters, may produce "birdies"
when playing these files - these birdies are not produced by the
DSP.)

(To play these clips, your web browser will have to support
sound files, and your computer will need a sound card and
speakers. If you have a sound card but your browser doesn't
support sound, you can always download these .WAV files and then
play them later, outside of your browser.)

W9GR uses his
own DSP-3 all the time, and says, "Once I was moving some
things around in the shack and I didn't have the DSP-3 in line. I
had this terrible feeling of 'nakedness' - that if a carrier came
on the frequency, I would actually hear it! And if a weak station
came on, I would actually have to listen to the noise!" Don't go naked - "cover yourself"
with a W9GR DSP-3!

It's best to be able to leave a DSP in line all the time,
rather than waiting for noise or interference to appear before
switching it in. The DSP-3 has been optimized to sound good with
both strong and weak signals. Many hams have complained about
other DSPs, which add resonances, strange audio tones, or
"rain barrel" sound effects to voice signals. Because
of these unpleasant artifacts, some hams leave these other DSP
units switched "out" until they are really needed.

Thousands of amateurs have built the W9GR digital signal
processor since it first appeared as a feature article in the
September 1992 issue of QST. Now an even more powerful and
versatile version of the DSP has been developed, and it is still
low cost. You can save money by building this kit yourself and
have a DSP superior to units costing twice as much! Even the high
priced DSPs do not have the ability to decode CTCSS and DTMF
tones!

Brief Description:

The W9GR DSP-3 filter is a DSP audio filter which goes between
your receiver's audio output and your loudspeaker or headphones.
A LED display indicates audio level, or in the tone decoder modes
it indicates DTMF and CTCSS tones. Modes are selected by a front
panel rotary switch, and options are selected by a rear panel
toggle switch. The DSP operates from your 12 volt DC power supply
(not furnished).

The W9GR DSP-3 filter hardware uses a 13 bit A/D and D/A
converter with switched capacitor filters for antialiasing and
analog reconstruction. This results in a much wider dynamic range
than earlier W9GR DSP filters, which used 8 bit converters. The
primary advantage to having more bits is for CW operators: the
ability to pick out weak CW signals amidst strong QRM.

The first three DSP functions are different combinations of
noise reducers and automatic notch filters, using the Widrow-Hoff
LMS adaptive filtering algorithm. The noise reducer modes are
most effective against hiss and thermal noise but also reduces
impulse noise and static crashes. These modes reduces listener
fatigue and are recommended for long-term monitoring. The
automatic notch mode eliminates multiple carriers very quickly,
within a few milliseconds. Tuner-uppers, CW interference,
carriers, and other forms of undesired audio tones are quickly
eliminated. If a carrier comes on your frequency, all you will
hear will be a subtle "click" as the automatic notch
acquires.

These three modes include a defeatable digital AGC, which
keeps the output level constant over variations of up to 30 dB.

A selection of FSK filters improves copy of RTTY, AMTOR, HF
packet, etc. in the presence of noise or QRM.

A special SSTV filter improves performance in that mode
without group delay distortion.

A DTMF decoder uses the LED display to tell you what
"touch tones" you are hearing. The last 16 decoded DTMF
tones can be "played back" from the DSP's memory.

A CTCSS decoder uses the LED display to tell you what
"PL" tones are being used. The last 16 different
decoded CTCSS tones can be "played back" from the DSP's
memory.

There are seven CW filters with various center frequencies and
bandwidths. Any of these filters can be tuned down to as low as
70% of the nominal center frequency.

The CW, FSK, narrow voice, and SSTV filter firmware programs
are all linear phase bandpass filters. Linear phase filtering,
which is a significant advantage of DSP, allows filter bandwidth
to be narrower than conventional filtering for a given maximum CW
speed or data rate.

The parts kit includes a finished double sided printed circuit
board with silk screen and solder mask, all PC board and front
panel components, IC sockets, and a CPU chip preprogrammed with
the DSP firmware. A cabinet and DC power supply are not included
with the basic kit.

For those who prefer not to do their own metalwork, a custom
made steel cabinet with silk screening is available.

We recommend that builders of this kit should be able to
solder, identify components, and construct a PC board from a
schematic and parts list.

The size of the box (less protuberances) is 1.5" high by
5.5" wide by 6" deep.

This document is for informational purposes only. QUANTICS
MAKES NO WARRANTEES, EXPRESS OR IMPLIED, IN THIS SUMMARY.

Here's what the back of the unit looks like:

And here is the all-important view of the real
"guts" of the W9GR DSP-3:

To order the DSP-3, please send us a prepaid order via the
regular mail (you know, the slow US Postal service, a.k.a.
"snail mail"). We are too small to take credit cards
and/or to offer an 800 number for telephone orders. An order form
follows - to make things easy, you can print it out (with a fixed
width font such as Courier), fill it out, and mail it in. REMINDER: the DSP-3 is sold out -
please do not send in this order form!

E-mail: (to inform you when your unit ships. You will NOT be spammed.)

_____________________@______________
Address: ____________________________________________
City, State,
Zip: ____________________________________________
Item Price Quantity Total
DSP-3 Kit $149.00 _____ _____
Custom metal cabinet for DSP-3 $19.00 _____ _____
(does not fit earlier kits)
California residents add 7.375% tax _____
Shipping & Handling _____
In the USA and Canada:
$7.00 for one or two kits with or without cabinet;
$3.50 for each additional kit with or without cabinet.
Outside the USA and Canada:
$20.00 for one kit with or without cabinet;
$10.00 for each additional kit with or without cabinet.
For cabinets ordered separately in the USA & Canada:
$5.00 for the first cabinet; $2.50 for each additional cabinet.
Outside the USA and Canada:
$15.00 for the first cabinet; $7.50 for each additional cabinet.
Total enclosed _____
All prices quoted are for U. S. funds drawn on a U. S. bank and are
subject to change without notice. California residents must add 7.375%
sales tax. Send orders to:
QUANTICS
P. O. Box 2163
Nevada City, California 95959-2163

What if
I build it and it doesn't work?

There are extensive troubleshooting instructions
included with the kit documentation. But, if that isn't
enough to help you get it going, we do have a "flat
rate" debugging service available. For a flat rate
of $40.00, we will get the unit working for you. Abuse is
excepted! This offer does not apply if you have driven
over the unit with a backhoe! Most of the time, we find
that the problem is defective soldering. But, if we find
that there was a bad part supplied with the kit, we will
return the debugged unit to you, with your $40.00 check
uncashed. See details in the DSP-3
Kit Instructions.

What do
users say?

Absolutely bloody AWESOME!.............OH BOY!! I am
not kidding: this filter is what I've been looking for
for YEARS! It gets rid of all the TV and computer birdies
I have here (I live in a densly populated suburb where
the average Yank would get the screaming abdabs from all
those people around him). The next thing was to have a
real test of what it can do, so I listened on 40m. As
you'll know, 40m is QRM alley here in Europe....not any
more! Of course it's not as good as filtering at IF, but
what the hell - my IC706 can cope now, and so can my
ears. The noise reduction is a blessing, but the
brick-wall audio filters for SSB or CW are just bloody
fantastic. I was able to copy weak CW signals that were
buried in the crud. Then the REAL test: I hooked it up to
my 80m DC receiver...erm.....is this my trusty old
"Sudden"?? Once again.....AMAZING! If you want
a new slogan: "Don't spend $$$$$$$$ on a new
rig...get a DSP III and keep your wife happy too"
...this is one serious bit of equipment that everyone
needs! 73, Pete PE1MHO/G7ECM

Dave, My DSP-3 arrived as scheduled on 5 March. Just
found the time to complete the project today. Every thing
works GREAT!! Really enjoyed assembling this project. All
parts were within specified tolerances and circuit board
construction was fabulous. The instruction sheet was
complete and easy to understand. I've been building and
repairing ham gear and electronic devices/systems since
1964 and your DSP 3 qualifies as one of the best kits I
have ever constructed. Thanks again for a quality product
. 73's from foggybottom radio WB4PDY Larry M. Graham

David, Kit went together in 2 nights, it works
perfectly, construction was soo easy, its a great little
unit only thing I did was bury the IC mounts under rubble
and soldered the IC's straight to the board =0( , but it
still works to spec regardless. It is a really nice
quality product that works well at a great price.
Everything was to what I expect from our suppliers and
boardhouses where I work (quality).. Thanks again Dave,
Sincerely, Collin A Dvorak K7AAB

Hi Dave, I am really impressed with the performance of
DSP III. Using a noise input and an audio spectrum
analyser ( Freq51 software with a Sound Blaster 16 ) I
checked each mode which were all as advertised. The SSTV
mode does a great job on cleaning up a WEFAX signal from
the Tokio Typhoon station JMH5 on 18.220 MHz, it cleaned
out the low frequency noise and gave a much cleaner plot.
73 de N7IVM

Dave, I finally found enough free time and put my DSP
kit together. I've got to tell you, I'm impressed. All
the parts were there. The circuit board is professionally
made. The instructions were good. It all fits in the
cabinet. The thing looks great. And, to top it off, it
worked the first time I turned it on. I'm impressed! I'm
still learning how to use the DSP. After 30 years of
doing this kind of thing "by ear," it's going
to take a while to get used to this new approach. I
certainly have noticed how easily the DSP disposes of,
lets say, tuners. 73... Peter, AE1T

Dave, The box came today around lunchtime. I was all
primed for it by downloading the manual earlier. Even
with taking several breaks for meals nets, etc., the unit
was assembled by 7 PM :>) What a great little unit!
Beautiful engineering and quality parts. There were
absolutely no difficulties encountered and it worked
perfectly the minute I powered the DSP-3 on. I could copy
signals on 160 meters that were virtually impossible; I
found several stations that I could switch the unit in
and out and verify the effectiveness. Congratulations,
Dave, on a very worthwhile device (and you may quote me,
HI). Don't forget to join us on 160 meters, Wednesday
nights. 73, Troy, W6HV

What are
the differences between the DSP-1, DSP-2, and DSP-3? And,
can I upgrade my DSP-1 or -2 to a DSP-3?

The DSP-1 and its close cousin the DSP-2 unfortunately
cannot be upgraded to the DSP-3. I made too many changes
in both hardware and software. These changes were
necessary to add additional capabilities to the DSP-3
design, which is substantially different from the earlier
units.

I changed the audio codec chip from an 8 bit unit to a
13 bit device, which adds another 30 dB of audio dynamic
range. But, the 13 bit codec has serial I/O whereas the
earlier 8 bit codec was parallel. Also, the 13 bit codec
forces the sampling rate to be lower, which had major
effects on the software. You get the idea - too many
changes. (But, I suppose that is better than changing a
resistor value and calling it a new model!)

The differences between the DSP-2 and the DSP-3 are:

1. 13 bit audio codec instead of 8 bits. This means a
much wider dynamic range, which is especially important
for CW where you may have a strong interfering station.

2. Optional AGC in the LMS adaptive modes.

3. Software AGC in the LMS adaptive modes, which means
that the adaptive filters behave the same regardless of
audio input level.